This proposal requests support for a Keystone Symposia meeting entitled Chemokines and Leukocyte Trafficking in Homeostasis and Inflammation, organized by William A. Agace, Sirpa Jalkanen and Sergio A. Lira, which will be held in Breckenridge, Colorado from January 8 - 13, 2012. The organized trafficking of leukocyte subsets through the tissue compartments of the body is critical to the generation of innate and adaptive immune responses and for normal organ immuno-surveillance; however, when misguided, such processes can promote uncontrolled inflammation resulting in tissue pathology. It is now well established that cellular adhesion and chemokine receptors play a central role in regulating tissue-specific leukocyte migration. Recent studies have started to unravel the complex mechanisms underlying the expression of these receptors on lymphocytes and highlight the importance of the local lymph node environments and migratory dendritic cells in the induction of peripheral tissue homing receptors. While immunologists have traditionally tended to focus on primary and secondary lymphoid compartments to study immunological processes and immune cell interactions, there is a growing realization that many, if not most, of our immune cells are located in peripheral tissues and that each of these sites possess unique immunological characteristics. The Keystone Symposia meeting on Chemokines and Leukocyte Trafficking in Homeostasis and Inflammation will bring together scientists and clinicians with expertise in immune cell migration, cellular adhesion/chemokine receptor regulation and tissue specific leukocyte trafficking with a focus on the peripheral tissue compartments in health and disease. PUBLIC HEALTH RELEVANCE: Leukocytes - white blood cells - have a chief function of protecting the body against microorganisms that cause disease. The organized trafficking of leukocyte subsets through the tissue compartments of the body is critical to the generation of immune responses and for normal organ immuno-surveillance; however, when misguided, such processes can promote uncontrolled inflammation and result in disease. The overall aim of the Keystone Symposia meeting on Chemokines and Leukocyte Trafficking in Homeostasis and Inflammation is to highlight the importance of tissue and micro-environmental context in the regulation of immune cell trafficking, with a particular focus on peripheral tissue compartments and the underlying mechanisms regulating the specificity of lymphocyte homing.